This invention relates to a mask (photomask) for use in transferring a fine pattern in the manufacture of semiconductor elements or the like and further relates to a mask blank being a base of such a mask.
With the increase in fineness of circuit patterns of semiconductor elements or the like, the tolerance between designed and measured pattern line widths of photomasks has become much smaller. As the degree of integration of semiconductor integrated circuits has increased, the design rule in the process of manufacturing those circuits has become stricter and more and more stringent demands have been made on the CD (Critical Dimension) uniformity and the CD linearity.
Techniques intended to satisfy such demands are disclosed in, for example, U.S. Pat. No. 6,472,107 (Patent Document 1) and Japanese Unexamined Patent Application Publication (JP-A) No. 2005-62884 (Patent Document 2). The technique disclosed in Patent Document 1 is a method of using a hard mask pattern, instead of a photoresist pattern, in etching a chromium layer for improving the CD uniformity and the CD linearity of a photomask. It is disclosed that use is made of silicon (Si), Ti, TiW, W, TiN, Si3N4, SiO2, SOG (Spin On Glass), or the like as a substance constituting a hard mask used for forming the hard mask pattern.
The technique disclosed in Patent Document 2 is an improvement of the technique disclosed in Patent Document 1. This technique provides a mask blank comprising a hard mask having an advantage such that, while maintaining the advantage of the above hard mask pattern, since it is more conductive, electron beam writing can be performed well and, further, it can have a large etching selectivity with respect to a chromium light-shielding film. It is disclosed that use is made of Mo, MoSi, MoSiON, or the like as a substance constituting the hard mask.